April 2015 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Trying to write/read value at PCI BAR address from Kernel Space
by Robert Clove April 28, 2015

April 28, 2015

Hi, I am trying to write and read PCI BAR address but not getting the expected output. I am using the ioremap api to get the address. Any leads will be fruit full. Regards

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Network Device Driver Interface
by sahil aggarwal April 28, 2015

April 28, 2015

Hi I enabled sampling on net_dev_queue and net_dev_xmit using perf_event_open(). This is what i get for cmd: ping google.com -c 1 TID:21608 PID:21608 TIME:1022501870535899 CPU:5 DEV_QUEUE Skb: 0xffff880fc6389000 Len:98 TID:21608 PID:21608 TIME:1022501870541280 CPU:5 DEV_QUEUE Skb: 0xffff880fc6389000 Len:98 TID:21608 PID:21608 TIME:1022501870119689 CPU:7 DEV_QUEUE Skb: 0xffff880fc6389000 Len:70 TID:21608 PID:21608 TIME:1022501902225838 CPU:5 DEV_QUEUE Skb: 0xffff880fc4156100 Len:86 TID:21608 PID:21608 TIME:1022501870128677 CPU:7 DEV_XMIT Skb: 0xffff880fc6389000 Len:70 Ret:0 TID:21608 PID:21608 TIME:1022501870545283 CPU:5 DEV_XMIT Skb: 0xffff880fc6389000 Len:98 Ret:0 TID:21608 PID:21608 TIME:1022501870547378 CPU:5 DEV_XMIT Skb: 0xffff880fc6389000 Len:98 Ret:0 TID:21608 PID:21608 TIME:1022501902232222 CPU:5 DEV_XMIT Skb: 0xffff880fc4156100 Len:86 Ret:0 TID:21608 PID:21608 TIME:1022501870132327 CPU:7 DEV_RECV Skb: 0xffff880fc6389000 Len: 56 TID:21608 PID:21608 TIME:1022501902235039 CPU:5 DEV_RECV Skb: 0xffff880fc4156100 Len: 72 TID:21608 PID:21608 TIME:1022501870125880 CPU:7 DEV_RX Skb: 0xffff880fc6389000 Len: 56 TID:21608 PID:21608 TIME:1022501902229768 CPU:5 DEV_RX Skb: 0xffff880fc4156100 Len: 72 Here, net_dev_queue is called multiple times for same skb with changed length. What i understood till now reading this: http://www.cubrid.org/blog/dev-platform/understanding-tcp-ip-network-stack/ was that skb received by device driver from IP layer is queued by __dev_queue_xmit(): tracepoint net_dev_queue() exist here and transmitted to network device by dev_hard_start_xmit(): tracepoint net_dev_xmit() exist here. So, what is making it to queue skb again and what data it is adding to skb.? Thanks Regards

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How to traverse all file struct
by cmqycmqy April 28, 2015

April 28, 2015

I want to travese(find out) all opened file struct, but the s_files in struct super_block is not exit any more.how can i do that? why i want to do this is that i want to find out all process that have open that file. Is there any suggestion?

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Re: Question about DC-DC frequency handling
by Stefan Wahren April 27, 2015

April 27, 2015

Hi, > Michael Turquette <mturquette(a)linaro.org> hat am 26. April 2015 um 21:07 > geschrieben: > > > Quoting Stefan Wahren (2015-04-26 07:31:30) > > Hi, > > > > i'm current working on a regulator driver which should be able to change > > DC-DC > > clock frequency. > > > > Now here is my question. What is the prefered way to implement the clock > > handling? > > Fun question. I have a question for you: who are the consumers of this > DC-DC? Do the downstream, consuming devices care about "clock rate" of > your regulator? > > I'll hazard a guess that they do not care. DC-DC switching frequency is > an important aspect of power supply design, but switching frequency of a > power supply is not controlled by the clock framework in any example > that I am aware of. yes the consumers don't care. My intension for changing the switching frequency is to avoid interferences on HF band. > > > > > Option A): > > > > The regulator driver handles all internally (select clock source, set > > frequency). > > Mark should weigh in on this, but I think option A is correct. Maybe > something like regulator_set_mode could program your switching > frequency? A runtime configuration isn't necessary. In a earlier discussion we decided to use a devicetree property. Thanks Stefan

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Semaphore and Spinlock
by Abhishek Bist April 27, 2015

April 27, 2015

[ Semaphores are a bit like spinlocks, except the holder of a semaphore is a process, not a CPU. ] This is a very first line that is bein written on the description of semaphore on kernel newbies.So what are the different parameter that could justify this statement or the way it could be justified and understood.

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Structure declaration without its members variables
by harshkdev April 27, 2015

April 27, 2015

Hi, What does this syntax means in file Arch/arm64/include/asm/kvm_asm.h struct kvm; struct kvm_vcpu; Generally we declare structure and its member at same place. Regards Harsh Jain

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How to get kernel header from my kernel source tree?
by tianlilai April 27, 2015

April 27, 2015

Hi,Everyone: I have updated the kernel from v2.6.32 to v2.6.36 using my kernel source tree(v2.6.36). so I must provide the new kernel header to the developers of the device driver. How can I get the kernel header from my kernel source tree which the version is v2.6.36? Thanks very much!

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mmc card write protect solution
by xiaoqiang zhao April 27, 2015

April 27, 2015

Hi, there: Is it possible to send CMD28(or CMD29) from userspace through ioctl to enable(or disable) write protected of a mmc block ? Looking forward to your reply!

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Re: Write and understand Assembly code in .S file for ARM
by harshkdev April 27, 2015

April 27, 2015

Hi, Coranac ARM link is very good thanks :) On 19 Apr 2015 18:45, victorascroft(a)gmail.com wrote: > > Hi, > > On 15-04-19 17:46:20, harshkdev wrote: > > Hi, > > > > Please refer some online tutorials or pdf books to write and understand assembly code written in .S file. > > Get Arm System Developer's Guide by Andrew Sloss, Dominic Symes and > Chris Wright. > > And for a basic understanding, refer the below links > http://www.toves.org/books/arm/ > http://www.coranac.com/tonc/text/asm.htm > > - Sanchayan > > > > > Regards > > Harsh Jain > > _______________________________________________ > > Kernelnewbies mailing list > > Kernelnewbies(a)kernelnewbies.org > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

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task deactivation
by Mustafa Hussain April 26, 2015

April 26, 2015

what the function deactivate_task() exactly do ? thanks in advance.

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